1. Field of the Invention
The present invention pertains to the control of electromagnetic emissions from an electronic device and, more particularly, from an integrated circuit device.
2. Description of the Related Art
An integrated circuit (xe2x80x9cICxe2x80x9d) can emit or radiate electromagnetic (xe2x80x9cEMxe2x80x9d) waves directly from the die on which the actual circuits are formed. Once the EM emissions radiate into the open area of a computing system""s chassis, it can be very difficult to contain. The EM emissions can leak from the chassis into the surrounding environment. These emissions can therefore cause a variety of significant problems when the ICs are employed in computing system. The emissions can conceivably generate electronic noise in neighboring devices that interfere with their operation. Also, the Federal Communications Commission (xe2x80x9cFCCxe2x80x9d) regulates the amount of EM emissions from a variety of commercially sold products, and emissions from an IC, e.g., the processor of a computing system, can cause the computing system to fail FCC emission requirements.
Current techniques address the EM emissions problem in a variety of ways. One approach is to design the IC to minimize the amount of EM radiation that is emitted. However, IC design frequently involves trade-offs among competing considerations. Performance or other types of considerations sometimes take precedence. It can also be difficult to estimate the level of EM emissions from a particular IC design until the IC design is fully embodied in an operational prototype. But once the IC design has been reduced to practice, there typically is very little that can be done to mitigate the EM radiation from the IC.
Another conventional technique adds EM shielding and gasketing around the inside of the chassis that contains the IC to prevent the EM emissions from leaking. While that technique can be effective, it can add a relatively significant amount to the cost of manufacturing a computing system.
It would be desirable to reduce the problem of EM radiation associated with electronic systems in a cost effective manner.
Accordingly, the invention includes a method and apparatus for shielding electromagnetic emissions originating from an integrated circuit. In one embodiment the invention provides an apparatus that includes a packaged integrated circuit. The package encloses at least one conductive plane, and at least a portion of the surface of the package is absent to expose at least a portion of the conductive plane. An integrated circuit die is mounted to the package. A heatsink thermally contacts the integrated circuit die. The heatsink includes a base and a projecting portion extending from the base to electrically couple to the conductive plane, the projecting portion defining a recess positioned over the integrated circuit die to enclose, in conjunction with the package, the integrated circuit die.
In another embodiment, the invention provides an apparatus that includes a heatsink that includes a base portion and a projecting portion having sides extending from the base portion, the projecting portion defining a recess for positioning over an integrated circuit die. The apparatus may further include a package for mounting the integrated circuit die, the package enclosing at least one conductive plane, at least a portion of a surface of the package being absent to expose at least a portion of the conductive plane; and wherein the heatsink is electrically coupled to the conductive plane through the projecting portion.
In another embodiment the invention provides a method that includes electrically coupling a heatsink and a conductive plane of an integrated circuit package thereby providing a structure to limit electromagnetic emissions from an integrated circuit die mounted in the package.
In another embodiment the invention provides a method of making a heatsink for use in controlling electromagnetic emissions from an integrated circuit. The method includes forming a recessed portion in a surface of the heatsink, the recessed portion including a thermal engagement portion for thermally engaging an integrated circuit die. The recessed portion has a top surface and side walls, the side walls providing an engagement surface for electrically coupling to a package holding the integrated circuit die.
In another embodiment the invention provides a method for controlling electromagnetic emissions from an integrated circuit die mounted in a package, that includes thermally engaging the integrated circuit die with at least part of a recessed portion of a heatsink; and electrically connecting a projecting portion of the heatsink, which defines the recessed portion, to a conductive plane of the package, thereby providing a Faraday cage defined by a heatsink and the conductive plane.